Simplify the following expression: $y = \dfrac{4q}{5} + \dfrac{-9q}{5}$
Since the expressions have the same denominator we simply combine the numerators: $y = \dfrac{4q - 9q}{5}$ Combine like terms: $y = \dfrac{-5q}{5}$ Simplify by dividing numerator and denominator by 5: $y = \dfrac{-q}{1}$ $y = -q$